1. Field of Invention
The present invention relates to a positioning structure, and particularly to a disc positioning structure of an optical disc drive.
2. Description of the Related Art
Optical discs have advantages such as enormous memory capacity, convenience to store, long lifetime of data keeping, low price and durability of stored data. Along with such advantages, currently optical discs are gradually replacing the conventional magnetic storage medium and have become an indispensable optical storage medium for modern people.
For modern optical disc drives, in terms of the structure positioning a disc onto a disc-carrying mechanism on a turntable, there are a sliding cone positioning structure and a multi-claw positioning structure. Although the sliding cone positioning structure, in general speaking, is able to provide higher positioning accuracy, it has disadvantages of structure complexity and higher cost. Therefore, the manufacturers of optical disc drives do not prefer the sliding cone positioning structure.
FIG. 1 is an exploded diagram of a conventional disc positioning structure assembled with an optical disc, which uses a multi-claw positioning structure. Referring to FIG. 1, a disc positioning structure 100 includes a carrier plate 110, a driver 120, a spin shaft 130 and a turntable 140. The driver 120 is disposed on the carrier plate 110 while the spin shaft 130 is disposed at the center of the driver 120 for driving the turntable 140 to turn. A fixing portion 142 is disposed at the center of the turntable 140. The spin shaft 130 inserts into the fixing portion 142 of the turntable 140 to hold the turntable 140 on the driver 120. In addition, independent five locking claws 144 are disposed on the turntable for holding an optical disc 200 onto an upper surface 140a of the turntable 140 in the disc positioning structure 100.
FIG. 2 is a section view showing an optical disc held on a turntable by locking claw. Referring to FIGS. 1 and 2, the optical disc 200 is desired to hold onto the turntable 140, a circle opening 210 at the center of the optical disc 200 is aligned with the center of the turntable 140 first, then pressing down the optical disc 200 toward the turntable 140. Due to an unavoidable offset between the centerline of the circle opening at the optical disc 200 and the centerline of the turntable 140, a displacement or a deformation caused from the locking claws 144 will occur as the optical disc 200 is pressed down. After that, by means of a displacement/deformation restoring-force of the locking claws 144, the optical disc 200 is shifted to align with the centerline of the turntable 140 and snapped on the turntable 140.
In more detail, as the optical disc 200 is placed onto the turntable 140 from the top of the turntable 140, usually only on one side of the opening 210 thereof is snapped into one of the locking claws 144 first, then the following pressing makes the circle opening 210 in sequence to be snapped into the rest locking claws 144. Since a positioning deviation occurs as the circle opening 210 of the optical disc 200 is snapped into the first claw of the locking claws 144 and there are no linkage between any two locking claws in the prior art, the produced deviation of the optical disc 200 is corrected by the first locking claw 144 only. While the rest locking claws are relatively off-duty to correct the deviation of the optical disc 200, so that the positioning performance of the prior art is poor and a serious offset error between the optical disc 200 and the optical disc drive will occur. When the optical disc 200 is poorly positioned, the servo control system of the optical disc drive is likely to be out of order.
In addition, most of the locking claws 144 are fabricated by molding. Due to the inaccuracy of molding manufacture, each one of the locking claws 144 may have different manufacturing tolerance from themselves that contributes a resulted positioning error from a desired positioning accuracy.
In summary, to make a conventional disc positioning structure in multi-claw centering mode having a less positioning error, it requires a more precise manufacturing technique and needs more sampling parts to maintain the production quality. Consequently, this leads to a high production cost.